An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. A cleaning fan blows air through the sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a residue system, which may utilize a straw chopper to process the non-grain material and direct it out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
To remove crop material from the field, the header of the combine harvester may be equipped with a cutter, such as a cutter bar assembly, having many sharp cutting elements that reciprocate sidewardly, relative to a forward direction of travel, to sever the crop material from the field before entering the feeder housing. The header may also include a rotating reel with tines or the like to sweep crop material toward the cutting elements.
To better follow the ground during harvesting, many headers include a flexible cutter bar assembly which can flex during travel of the vehicle to more closely follow the contour of the ground when, for example, the vehicle encounters uneven terrain. To flex, the cutter bar assembly may include one or more flexible segments which carry the cutting elements and are connected to arms which can move up and down responsively to forces from the ground, which causes flexing of the flexible segments and vertical movement of the carried cutting elements.
One particular problem encountered by headers including flexible cutter bar assemblies arises due to the movable nature of the cutting elements in relation to the tines of the reel. In many configurations, the cutting elements have the ability to flex a significant distance, such as 3 inches, vertically toward the reel tines; the top position where the cutter bar is able to flex can be referred to as the top of the “flex range” of the cutter bar. To avoid the tines being clipped off by the cutting elements when the cutter bar reaches the top of the flex range, the tines must be kept, at least, above the top of the flex range. In order to keep the tines above the top of the flex range so the tines do not get clipped off by the reel during maximum flexure, the reel may be positioned so that the lowest position of the tines is above the top of the flex range as the vehicle is harvesting. In such a configuration, reel performance may be poor due to the distance between the tines and the cutting elements being too large to efficiently move crops toward the cutting elements when the cutter bar is at its normal operating position, e.g., 3 inches below the top of the flex range. To improve reel performance, some headers are equipped with reels that can move up and down responsively to flexure of the cutter bar. One particular problem with such known configurations is that there can be a delay between the cutter bar flexing and the reel moving, which risks some of the tines being clipped off by the cutting elements, and the constructions may be complex.
What is needed in the art is a header which can overcome some of the previously described disadvantages of known headers.